Oftentimes advertisers use keyword advertising to market their goods and services to consumers. Keyword advertising uses specific words and phrases to target consumers. For example, if a consumer searches a particular keyword, targeted advertising banners will be displayed based on the searched keyword. Advertisers seek to generate increased consumption of their goods or services through images or messages designed to attract consumers. Online advertising may be delivered, for instance, by an ad server, on search engine results pages, via banner ads, and/or in text ads. Advertisers bid on keywords or phrases so their ads will be displayed to consumers when the keywords or phrases are used. Advertisers also track the success rates of keywords in the advertising marketplace. For example, impressions refer to the number of times an advertisement is displayed. Each time the advertisement is displayed it is counted as one impression. Tracking how keywords perform is important to advertisers because it is a key way in which Web advertising is accounted for and paid for.